The convergence of the mobile telephone network, the static telephone network, and the IP network provides a myriad of communication options for users. If one seeks to contact another individual, he or she may do so by electronic mail or e-mail, instant messaging, wired or wireless telephone, personal computer, pager, personal digital assistant or PDA, and Unified Messaging or UM systems, to name but a few. With so many options, it is difficult, if not impossible, to determine which option at a given point in time will provide the caller with the highest likelihood of contacting the desired individual or callee. Trial and error and guesswork are the typical techniques used to contact the callee, which more often than not leads to a waste of time and frustration on the part of the caller.
Various attempts have been made to provide a presence aware network, which would temporally track an individual's usage of selected communication devices to provide a contactor with the highest likelihood of contacting the individual. Most recently, the Session Initiation Protocol or SIP (which is a simple signaling/application layer protocol for data network multimedia conferencing and telephony) has been developed to provide a degree of presence awareness in a communication network. Although other protocols are equally supportive of presence concepts, SIP provides an illustrative basis for the present invention.
In SIP, end systems and proxy servers can provide services such as call forwarding, callee and caller number delivery (where numbers can be any naming scheme such as a conventional URL format), personal mobility (the ability to reach a callee under a single, location-independent address even when the callee changes terminals), terminal-type negotiation and selection (e.g., a caller can be given a choice on how to reach the callee), mobile phone answering service, terminal capability negotiation, caller and callee authentication, blind and supervised call transfer, and invitations to multicast conferences.
To provide these varied services, SIP uses a relatively simple message system, namely an “INVITE” message (with the caller's codec preferences) and an “OK” message (with the callee's codec preferences), and various software entities, namely registrars which maintain a map of the addresses of a given user at the current time, proxies which perform call routing, session management, user authentication, redirect functions, and routing to media gateways, redirect servers which perform a subset of forwarding functions, and SIP location servers which maintain user profiles and provide subscriber registration. “Registration” is a mechanism whereby a user's communication device registers with the network each time he or she comes online and individual profiles are accessed that specify information for routing based on a number of different criteria.
Although SIP provides some degree of presence awareness, more presence awareness is desirable. A fundamental problem of existing implementations is a notification gap in human communication between live-call and messaging systems. Existing implementations integrate live-call scenarios on an extremely limited scope. They are generally characterized by static rules for terminating a call at the messaging system or by allowing the messaging system to launch a call. For example, to determine the message waiting status of a mailbox you must either log into the mailbox, or the mailbox must turn on a device-specific message-waiting lamp or other static indicator. Both of these mechanisms exemplify direct, deliberate action on the part of either the user or the system, which is typical of current systems. Current commercial messaging systems allow only primitive dynamic correlation of message notification, presence and current call context. Even the most advanced workflow engines and collaborative environments in data networks that use more dynamic presence data with mailbox status notification suffer from severe limitations in their scope of communications. They generally cannot interoperate with the public switched telephone network.